Monday, January 21, 2008

Frost flowers

Every autumn in the Ozarks, before the ground freezes, woodlands are awash in delicate ice formations called frost flowers. These fragile sculptures occur in shady areas, or in the morning hours before the sun has a chance to reach the floor.

Frost flowers are formed when the sap in certain plants freezes, thereby expanding in the stem and causing the formation of small fissures. Water is drawn up through the stem, but as it exits the cracks, it freezes upon contact with the air. As capillary action pulls more water through the stem, the ice is forced out of the cracks, curling into delicate "petals."

In the Ozarks, they only occur in a handful of species. Among them are ironweed and snakeroot, both fall blooming wildflowers. Every frost flower is different, some more ornate than others. They're extremely delicate, breaking at the slightest touch.

I missed seeing them this year, as I was in the middle of a move when they were forming (picture by Ozark native Peter Callaway). Next fall, girded with the knowledge of species composition in several Ozark woodlands, I'll make sure I'm in the woods on those late autumn mornings to take some photos of my own.

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